1. Field of the Invention
The present invention relates to signal processing circuits and systems. More specifically, the present invention relates to circuits and systems for providing automatic gain and offset control.
2. Description of the Related Art
Certain circuits, particularly analog-to-digital converters, require input signals which are centered within a predetermined range. This is problematic with respect to visible and infrared video systems where input signal levels may vary due to a variety of factors. In these systems, the input signal should be symmetrical to fully utilize the entire dynamic range of the system. This is achieved, in many cases, by AC coupling the input signal. While, for these systems, the average signal levels are centered, gain control must still be effected.
Gain and level (or offset) control may be achieved by manual adjustment whenever the input signal changes. However, this solution has been found to be unacceptable in some applications inasmuch as it requires operator attention and skill, operator controls and wiring for same.
Previous automatic gain control systems sensed peak levels or average levels. Using peak levels allows a small number of extreme signal samples or picture elements to reduce the gain of the majority of the samples, resulting in a low contrast image. A system based on average signal levels may allow a substantial number of picture elements to exceed the dynamic range of the system, resulting in lost information.
Thus, a need remains in the art for a circuit or system for automatically adjusting the gain and level of signals input to or output from an electronic circuit.